Darren Joliny, a popular 21-year-old with ambitions to travel the world, collapsed at the Alistair McCoist Sports Centre in Whitehills, East Kilbride on Saturday.
He was given CPR by paramedics but did not regain consciousness and was pronounced dead at Hairmyres Hospital.
Just hours before, he had been playing computer games, getting ready to meet friends.
Since his sudden death, tearful family members, including mum Kathleen, 49, dad Reza, 50, and sisters Maria, 25, Elena, 16 and 14-year-old Carla, have been gathering at the family home in the town.
They thanked the medical staff who looked after their "golden boy".
Darren, who was half-Iranian, was best friends with his cousin Jordan McCann, 20.
Jordan's dad – and Darren's uncle – local MP Michael McCann, who spoke on behalf of the family, said they were still trying to come to terms with the tragic news.
He said Darren's death may have been similar to Phil O'Donnell, the Scottish footballer who died after suffering cardiac arrest while on the pitch playing for Motherwell against Dundee United in December 2007.
Mr McCann said: "Darren was playing his PlayStation on Saturday morning and then ran across to the Ally McCoist Sports Centre to meet friends for a game of football.
"Twenty minutes later he collapsed and they couldn't bring him back.
"One of the nurses at the hospital mentioned it was may be another Phil O'Donnell situation – one of these tragic things that could have happened anywhere or any time but which can't really be explained."
He added: "My son Jordan and Darren were inseparable. They always said they would be best man at each others' wedding and we used to joke that they would both have to find someone daft enough to marry them first.
"That incredible big mop of hair meant you couldn't help but notice him and he always lit up a room."
"Darren was larger than life but that was just a part of his personality. The other part was a young man who was sensitive and cared deeply for others."
Darren attended St Andrews High School in East Kilbride before graduating with a BA Honours in Journalism at Glasgow Caledonian University last year.
He worked part time at fashion store Zara in the South Lanarkshire town.
Tributes have poured in for the graduate, known as Rufio, with shocked friends describing him as an, "absolute gem".
Darren was a huge fan of the combat sport mixed martial arts (MMA) and worked behind the scenes at MMA events organised by Glasgow-based On Top Promotions.
James Lake, of On Top Promotions, called Darren a "consummate profess-ional when helping us out with interviews and articles and was always willing to be involved in anything to gain experience in the industry".
He added: "You could tell that he was passionate about MMA."
A celebration of Darren's life will take place at 8pm tonight at the Heritage Loch in East Kilbride where loved ones will set off lanterns and balloons.
A post mortem will be carried out to establish the cause of death.
The funeral will be organised once the post mortem has been completed. Inquiries should be directed to John Donnelly at Heritage Funerals, on 01355 271717.
